Method and device for permanently repairing defects of absent material of a photolithographic mask

ABSTRACT

The present application relates to a method for permanently repairing defects of absent material of a photolithographic mask, comprising the following steps: (a) providing at least one carbon-containing precursor gas and at least one oxidizing agent at a location to be repaired of the photolithographic mask; (b) initiating a reaction of the at least one carbon-containing precursor gas with the aid of at least one energy source at the location of absent material in order to deposit material at the location of absent material, wherein the deposited material comprises at least one reaction product of the reacted at least one carbon-containing precursor gas; and (c) controlling a gas volumetric flow rate of the at least one oxidizing agent in order to minimize a carbon proportion of the deposited material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority under 35U.S.C. § 120 from U.S. application Ser. No. 15/441,678, filed on Feb.24, 2017, now U.S. Pat. No. 10,372,032, which claims priority to Germanpatent application 10 2016 203 094.9, filed on Feb. 26, 2016. The entirecontents of each of these priority applications are hereby incorporatedby reference.

TECHNICAL FIELD

The present invention relates to a method and a device for permanentlyrepairing defects of absent material of a photolithographic mask.

BACKGROUND

As a consequence of the constantly increasing integration density inmicroelectronics, photolithographic masks have to image structureelements that are becoming ever smaller into a photoresist layer of awafer. In order to meet these requirements, the exposure wavelength isbeing shifted to ever shorter wavelengths. At the present time, argonfluoride (ArF) excimer lasers are principally used for exposurepurposes, these lasers emitting at a wavelength of 193 nm. Intensivework is being done in regard to light sources which emit in the extremeultraviolet (EUV) wavelength range (10 nm to 15 nm), and correspondingEUV masks. In order to increase the resolution capability of waferexposure processes, a number of variants of the conventional binaryphotolithographic masks have been developed simultaneously. Examplesthereof are phase masks or phase shifting masks and masks for multipleexposure.

On account of the ever decreasing dimensions of the structure elements,photolithographic masks, photomasks or simply masks cannot always beproduced without defects that are printable or visible on a wafer. Owingto the costly production of photomasks, defective photomasks, wheneverpossible, are repaired. Two important groups of defects ofphotolithographic masks are, firstly, dark defects. These are locationsat which absorber or phase shifting material is present, but whichshould be free of this material. These defects are repaired by removingthe excess material preferably with the aid of a local etching process.

Secondly, there are so-called clear defects. These are defects on thephotomask which, upon optical exposure in a wafer stepper or waferscanner, have a greater light transmissivity than an identicaldefect-free reference position. In mask repair processes, these defectscan be eliminated by depositing a material having suitable opticalproperties. Ideally, the optical properties of the material used for therepair should correspond to those of the absorber or phase shiftingmaterial. The layer thickness of the repaired location can then beadapted to the dimensions of the layer of the surrounding absorber orphase shifting material.

The material deposited for the repair should satisfy at least twofurther requirements. Firstly, it should withstand a predefined numberof mask cleaning cycles substantially without alterations to itsconstitution, i.e. the optical properties and size. Secondly, a givennumber of wafer exposures should be able to be carried out with thedeposited material, without the stated properties of the depositedmaterial experiencing a significant change with regard to the adjacentabsorber or phase shifting material.

WO 2012/146647 A1 describes the deposition of a reference marking on aphotomask with the aid of a particle beam, a process gas and anadditional gas, which may be an oxidizing gas.

WO 2005/017949 A2 describes the deposition of material on a photomask byuse of an electron beam and TEOS (tetraethyl orthosilicate) or anorganic or inorganic precursor gas.

The US patent having the number U.S. Pat. No. 7,727,682 B2 describes therepair of a phase shifting layer with the aid of an electron beam andthe deposition gas TEOS. In order to protect the repaired location, in asecond process step, a chromium protective layer is deposited on thephase shifting photomask over the whole area with the aid once again ofan electron beam and of chromium hexacarbonyl.

The applicant has established that repaired locations of clear defectsmay be subject to a change in the course of the use of repairedphotomasks. The document cited last reveals that a location repaired bythe deposition of a suitable material has to be provided with aprotective layer.

However, applying a whole-area protective layer on a repaired mask inorder to cover one or more repaired locations is a time- andcost-intensive additional process step. Moreover, depositing thisadditional layer entails the risk that a layer that is not perfectlyuniform will produce a new defect of the repaired photomask.

The present invention therefore addresses the problem of specifying amethod and a device which enable a permanent repair of defects of absentmaterial of a photolithographic mask and avoid at least some of thedisadvantages discussed above.

SUMMARY

According to an exemplary embodiment of the present invention, thisproblem is solved by a method for permanently repairing defects ofabsent material of a photolithographic mask, the method comprising thefollowing steps: (a) providing at least one carbon-containing precursorgas and at least one oxidizing agent at a location to be repaired of thephotolithographic mask; (b) initiating a reaction of the at least onecarbon-containing precursor gas with the aid of at least one energysource at the location of absent material in order to deposit materialat the location of absent material, wherein the deposited materialcomprises at least one reaction product of the reacted at least onecarbon-containing precursor gas; and (c) controlling a gas volumetricflow rate of the at least one oxidizing agent in order to minimize acarbon proportion of the deposited material.

When depositing material from a carbon-containing precursor gas, inmethods and devices according to the prior art part of the carboncontained in the precursor gas, or of one or more carbon compounds, maybe inadvertently incorporated into the deposited material. During theexposure of a photomask having one or a plurality of correspondinglyrepaired locations of clear defects, the deep ultraviolet (DUV)radiation used for the exposure and/or the ozone arising from theambient gas during the exposure process, extract part of the carbonincorporated into the deposited material. Furthermore, a repeatedprocess of cleaning the repaired mask can likewise liberate part of thecarbon present in the deposited material. Both processes alter theproperties, in particular the optical properties, and/or the structureof the material deposited in the mask repair process.

A method according to the invention solves this problem by controlledoxidation of the precursor gas during the chemical reaction of theprecursor gas initiated by an energy source. The proportion of volatilecarbon-containing compounds that can leave the reaction site issignificantly increased as a result. As a consequence thereof, thefraction of carbon incorporated into the deposited material issignificantly reduced. As a result of the reduced carbon proportion, thematerial deposited for repairing a clear defect has a significantlyincreased long-term stability. It can withstand a predefined number ofexposure and cleaning cycles substantially without a change in itsoptical properties and its dimensions.

In this application, a reaction or a chemical reaction denotes a processin which one or more chemical compounds are converted into one or moreother compounds. In the context of this application, a dissociation of achemical compound is regarded as a special case of a reaction or of achemical reaction.

The expression “substantially” here, as at these places in thisdescription, denotes an indication of a measured variable within thecustomary error limits when using metrology according to the prior art.

According to a further aspect, the deposited material comprises a carbonproportion of <20 atom %, preferably <15 atom %, more preferably <10atom %, and most preferably <5 atom %.

During the deposition of a layer composed of a carbon-containingprecursor gas, the carbon proportion in the deposited material is in theregion of 20 atom % or higher. By additionally providing an oxidizingagent during the chemical reaction of the carbon-containing material, itis possible for a carbon proportion of the deposited material to besignificantly reduced. As a consequence thereof, the ageing process ofthe deposited material is drastically slowed down.

According to another aspect, the at least one carbon-containingprecursor gas comprises at least one metal carbonyl and/or at least onemain group element alkoxide.

Metal carbonyls can be used to correct clear defects of binaryphotomasks. A precursor gas in the form of a main group element alkoxidecan be used for repairing substrate defects of a transmissive photomaskand/or for repairing EUV masks. A carbon-containing precursor gas whichcomprises a metal carbonyl and a main group alkoxide can be used forcorrecting clear defects present on phase masks.

According to yet another aspect, the at least one metal carbonylcomprises at least one element from the group: chromium hexacarbonyl(Cr(CO)₆), molybdenum hexacarbonyl (Mo(CO)₆), tungsten hexacarbonyl(W(CO)₆), dicobalt octacarbonyl (Co₂(CO)₈), triruthenium dodecacarbonyl(Ru₃(CO)₁₂), and iron pentacarbonyl (Fe(CO)₅).

In accordance with yet another aspect, the at least one main groupelement alkoxide comprises at least one element from the group:tetraethyl orthosilicate (Si(OC₂H₅)₄, TEOS), tetramethyl orthosilicate(Si(OCH₃)₄, TMOS) and titanium tetraisopropoxide (Ti(OCH(CH₃)₂)₄).

According to one expedient aspect, the at least one oxidizing agentcomprises at least one element from the group: oxygen (O₂), ozone (O₃),water vapor (H₂O), hydrogen peroxide (H₂O₂), dinitrogen monoxide (N₂O),nitrogen monoxide (NO), nitrogen dioxide (NO₂) and nitric acid (HNO₃).

An oxidizing agent can be used independently of whether thecarbon-containing precursor gas comprises a metal carbonyl, a main groupelement alkoxide or a combination of a metal carbonyl and a main groupelement alkoxide.

According to yet another aspect, the at least one energy sourcecomprises at least one particle beam. In accordance with yet anotherexpedient aspect, the at least one particle beam comprises an electronbeam and/or a photon beam.

Both electron beams and photon beams can be finely focused, such thatthe area within which an electron beam and/or a photon beam initiate(s)a chemical reaction of the at least one carbon-containing precursor gasis very small. The spatial resolution when repairing local clear defectsis thus high.

The electron beam can have a resolution in a range of 0.4 nm to 10 nm,preferably 0.5 nm to 8 nm, more preferably 0.6 nm to 6 nm, and mostpreferably of 0.7 nm to 4 nm. Furthermore, the electron beam can have anenergy in a range of 0.05 keV to 5 keV, preferably 0.1 keV to 4 keV,more preferably 0.2 keV to 3 keV, and most preferably 0.4 keV to 2 keV.Furthermore, the electron beam can have a beam current in a range of 5pA to 100 pA, preferably 10 pA to 80 pA, more preferably 15 pA to 70 pA,and most preferably of 20 pA to 60 pA.

In a further aspect, the electron beam at a location to be repaired hasa dwell time in the range of 30 ns to 1 s, preferably 50 ns to 100 ms,more preferably 50 ns to 10 μs, and most preferably of 50 ns to 5 μs. Inaccordance with another expedient aspect, the electron beam has arepetition time in the range of 1 us to 10 s, preferably 10 μs to 1 s,more preferably 50 us to 300 ms, and most preferably 100 us to 100 ms.

The absent material can comprise at least one element from the group:absent material of at least one structure element of a binary mask,absent material of at least one structure element of a phase mask,absent material of at least one structure element of a photomask for theextreme ultraviolet wavelength range, absent material of a substrate ofa transmissive photolithographic mask, and/or absent material of ananoimprint technology mask.

The method according to the invention can advantageously be used forcorrecting clear defects of the various photomasks currently used and indevelopment.

Providing the at least one carbon-containing precursor gas and the atleast one oxidizing agent at the location of absent material can becarried out with a mixture ratio of 1:100, preferably 1:50, morepreferably 1:25, and most preferably 1:10.

It is expedient to provide at least ten times more particles of anoxidizing agent at a location to be repaired of a photomask thanparticles of a precursor gas. The oxidizing agent that provides oxygenensures that a highest possible proportion of volatile carbon-containingcompounds is formed during the chemical reaction of the precursor gas.

Providing the at least one metal carbonyl and the at least one maingroup element alkoxide can be carried out with a mixture ratio of 1:20,preferably 1:10, more preferably 1:7, and most preferably 1:5.

As a result of the oxidation of the precursor materials, during thedeposition process for repairing a clear defect of a phase mask, thecarbon proportion in the deposited material is reduced in comparisonwith deposited materials from the prior art. A sufficient stabilityagainst carbon-reactive mask cleaning processes can thus be achieved.For the same reason, it is possible to achieve a sufficient durabilityin relation to the exposure of the repaired mask in a wafer stepper orwafer scanner. For this purpose, in the case of the repair of phaseshifting masks—with the action of a corresponding oxidizing agent—asmall admixture of metal carbonyls to a precursor gas composed of a maingroup element alkoxide is already sufficient.

In accordance with one advantageous aspect, providing the at least onemain group element alkoxide and the at least one oxidizing agent at thelocation of absent material is carried out with a mixture ratio of1:100, preferably 1:50, more preferably 1:25, and most preferably 1:10.

In a manner similar to that for the ratio of metal carbonyl to oxidizingagent, it is advantageous to provide significantly more particles of anoxidizing agent at a location to be repaired of a photomask thanparticles of a precursor gas composed of a main group element alkoxide.

In one advantageous aspect, providing the at least one oxidizing agentis carried out with a gas volumetric flow rate in the range of 0.3 sccmto 10 sccm, preferably 0.5 sccm to 7 sccm, more preferably 1 sccm to 5sccm, and most preferably 2 sccm to 4 sccm.

The gas volumetric flow rate of the oxidizing agent can be set with theaid of a metering valve and/or by a change in temperature of the storedoxidizing agent. The metering valve can be realized in the form of amass flow controller.

According to one preferred aspect, providing the at least one metalcarbonyl at the location of absent material is carried out in a pressurerange of 10⁻⁶ mbar to 10⁻⁴ mbar, providing the at least one main groupalkoxide is carried out in a pressure range of 10⁻⁶ mbar to 10⁻⁴ mbar,and/or providing the at least one oxidizing agent is carried out in apressure range of 10⁻⁵ mbar to 10⁻² mbar.

In accordance with yet another aspect, providing the at least one metalcarbonyl at the location of absent material is carried out in atemperature range of −50° C. to +35° C., preferably −40° C. to +30° C.,more preferably −30° C. to +25° C., and most preferably −20° C. to +20°C. It is advantageous to adapt the temperature range for providing theat least one metal carbonyl to the metal carbonyl(s) used.

Providing the at least one main group element alkoxide at the locationof absent material can be carried out in a temperature range of −40° C.to +15° C., preferably −30° C. to +5° C., more preferably −20° C. to −5°C., and most preferably −15° C. to −10° C.

Material can be deposited at a rate of 0.01 nm/s to 1.0 nm/s, preferably0.02 nm/s to 0.5 nm/s, more preferably 0.04 nm/s to 0.3 nm/s, and mostpreferably 0.05 nm/s to 0.15 nm/s.

The photolithographic mask can comprise a phase mask, and providing theat least one precursor gas can comprise simultaneously providingchromium hexacarbonyl (Cr(CO)₆) and tetraethyl orthosilicate(Si(OC₂H₅)₄, TEOS).

A precursor gas comprising chromium hexacarbonyl and TEOS can be usedfor correcting a clear defect of a phase mask, in particular anattenuated phase shift mask. In association with a deposition step, adefect repair largely exhibiting long-term stability can be achievedwith this precursor gas combination. The deposition of a protectivelayer over the repaired and thus simultaneously over the entirephotomask is no longer necessary.

According to yet another aspect, a device for permanently repairingdefects of absent material of a photolithographic mask comprises: (a)means for providing at least one carbon-containing precursor gas and atleast one oxidizing agent at a location to be repaired of thephotolithographic mask; (b) at least one energy source for initiating areaction of the at least one carbon-containing precursor gas at thelocation of absent material in order to deposit material at the locationof absent material, wherein the deposited material comprises at leastone reaction product of the reacted at least one carbon-containingprecursor gas; and (c) means for controlling a gas volumetric flow rateof the at least one oxidizing agent in order to minimize a carbonproportion of the deposited material.

A device according to the invention enables the local deposition ofmaterial exhibiting long-term stability on a photomask, which materialsubstantially reproduces the optical properties of the materialsurrounding the defect. The deposited material can thus be adapted tothe dimensions of the defect.

According to a further aspect, the means for providing the at least onecarbon-containing precursor gas and the at least one oxidizing agentcomprises at least three supply containers each having at least onemetering valve and at least one gas feed line system having at least onenozzle near the location to be repaired, in order to provide at leastone first and one second carbon-containing precursor gas and at leastone oxidizing agent.

Finally, the means for controlling the gas volumetric flow rate of theat least one oxidizing agent can comprise a control unit configured tocontrol the gas volumetric flow rate of the at least onecarbon-containing precursor gas and of the at least one oxidizing agent.

DESCRIPTION OF DRAWINGS

The following detailed description describes currently preferredexemplary embodiments of the invention, with reference being made to thedrawings, in which:

FIG. 1 schematically illustrates a block diagram of some importantcomponents of a device which can be used for repairing clear defects ofa photomask;

FIG. 2 schematically has an excerpt from a photomask which has a defectof absent substrate material;

FIG. 3 reproduces the excerpt from FIG. 2 after the defect of absentsubstrate material has been partly repaired;

FIG. 4 represents the excerpt from FIG. 3 after the repair of the defectof absent substrate material;

FIG. 5 schematically has an excerpt from a binary photomask which has adefect of absent absorber material;

FIG. 6 illustrates FIG. 5 with the repaired defect;

FIG. 7 schematically represents an excerpt from a phase shiftingphotomask and/or a pure quartz mask which has a defect of absentabsorber material;

FIG. 8 shows FIG. 7 with the corrected defect; and

FIG. 9 reproduces a flow diagram of the method for repairing defects ofabsent material of a photolithographic mask.

DETAILED DESCRIPTION

Currently preferred embodiments of the device according to the inventionfor permanently repairing defects of absent material of aphotolithographic mask are explained in greater detail below on thebasis of the example of a modified scanning electron microscope.However, the device according to the invention is not restricted to theexample described below. As will be recognized without difficulty by aperson skilled in the art, instead of the scanning electron microscopediscussed it is possible to employ any scanning particle microscopewhich uses for example a focused ion beam and/or a focused photon beamas energy source. Furthermore, the method according to the invention isnot restricted to the use of the photomasks discussed by way of examplebelow. Rather, this method can be used for repairing any desiredphotolithographic masks. Furthermore, the application of the methodaccording to the invention is not restricted to the application tophotomasks. Rather, this method can be employed for repairing templatesfor nanoimprint technology or generally for correcting optical elementshaving defects of absent material.

FIG. 1 schematically shows essential components of a device 100 whichcan be used for permanently repairing samples 105 having defects ofabsent material. Here, the phrase “permanently repairing samples 105having defects of absent material” means that the material deposited forrepairing the defects has a significantly increased long-term stability,and that it can withstand a predefined exposure dose and a predefinednumber of cleaning cycles (e.g. at least 10) substantially without achange in its optical properties and its dimensions.

The sample 105 may be an arbitrary microstructured component orstructural part. By way of example, the sample 105 may comprise atransmissive or a reflective photomask and/or a template for nanoimprinttechnology. Furthermore, the device 100 can be used for repairing forexample an integrated circuit, a microelectromechanical system (MEMS)and/or a photonic integrated circuit which have/has defects of absentmaterial. In the examples explained below, the sample 105 is aphotolithographic mask 105.

The exemplary device 100 in FIG. 1 is a modified scanning electronmicroscope (SEM). An electron gun 115 generates an electron beam 127,which is directed by the elements 120 and 125 as a focused electron beam127 onto the photolithographic mask 105 arranged on a sample stage 110.

The sample stage 110 has micromanipulators (not shown in FIG. 1) withthe aid of which the defective location of the photomask 105 can bebrought beneath the point of incidence of the electron beam 127 on thephotomask 105. In addition, the sample stage 110 can be displaced inheight, i.e. in the beam direction of the electron beam 127, such thatthe focus of the electron beam 127 becomes located on the surface of thephotomask 105 (likewise not illustrated in FIG. 1). Furthermore, thesample stage 110 can comprise a device for setting and controlling thetemperature, which makes it possible to bring the photomask 105 to apredefined temperature and to keep it at this temperature (not indicatedin FIG. 1).

The device 100 in FIG. 1 uses an electron beam 127 as energy source 127for initiating a local chemical reaction of a carbon-containingprecursor gas. An electron beam 127 can be focused onto a small focalspot having a diameter of <10 nm. In addition, electrons that areincident on the surface of the photomask 105 cause hardly any damage tothe photomask 105, even if their kinetic energy varies over a largeenergy range. However, the device 100 and the method presented here arenot restricted to the use of an electron beam 127. Rather, any desiredparticle beam can be used which is able to bring about locally achemical reaction of a precursor gas at the point of incidence of theparticle beam on the surface of the photomask 105. Examples ofalternative particle beams are an ion beam, atomic beam, molecular beamand/or photon beam. Furthermore, it is possible to use two or moreparticle beams in parallel. In particular, it is possible simultaneouslyto use an electron beam 127 and a photon beam as energy source 127 (notshown in FIG. 1).

The electron beam 127 can be used for recording an image of thephotomask 105, in particular of a defective location of the photomask105. A detector 130 for detecting backscattered electrons and/orsecondary electrons supplies a signal that is proportional to thesurface contour and/or composition of the photomask 105.

By scanning or raster-scanning the electron beam 127 over the photomask105 with the aid of a control unit 145, a computer system 140 of thedevice 100 can generate an image of the photomask 105. The control unit145 can be part of the computer system 140, as illustrated in FIG. 1, orcan be embodied as a separate unit (not illustrated in FIG. 1). Thecomputer system 140 can comprise algorithms which are realized inhardware, software, firmware or a combination thereof and which make itpossible to extract an image from the measurement data of the detector130. A screen of the computer system 140 (not shown in FIG. 1) canrepresent the calculated image. Furthermore, the computer system 140 canstore the measurement data of the detector 130 and/or the calculatedimage. Furthermore, the control unit 145 of the computer system 140 cancontrol the electron gun 115 and the beam-imaging and beam-shapingelements 120 and 125. Control signals of the control unit 145 canfurthermore control the movement of the sample stage 110 by use ofmicromanipulators (not indicated in FIG. 1).

The electron beam 127 incident on the photomask 105 canelectrostatically charge the photomask 105. As a result, the electronbeam 127 can be deflected and the spatial resolution when recording adefect and when repairing the latter can be reduced. In order to reducean electrostatic charging of the photomask 105, an ion gun 135 can beused to irradiate the surface of the photomask 105 with ions having lowkinetic energy. By way of example, it is possible to use argon ionshaving a kinetic energy of a few 100 eV for neutralizing the photomask105.

In order to process the photomask 105 arranged on the sample stage 110,i.e. to repair the defects of said photomask, the device 100 comprisesat least three supply containers for three different processing gases.The first supply container 150 stores a first precursor gas, inparticular a first carbon-containing precursor gas. By way of example, amain group element alkoxide can be stored in the first supply container,such as TEOS, for instance. The second supply container 155 stores asecond carbon-containing precursor gas. The precursor gas stored in thesecond supply container 155 may be for example a metal carbonyl, forinstance chromium hexacarbonyl. The third supply container 160 stores anoxidizing agent, for instance oxygen. An oxidizing agent can comprisefor example an element from the group: oxygen (O₂), ozone (O₃), watervapor (H₂O), hydrogen peroxide (H₂O₂), dinitrogen monoxide (N₂O),nitrogen monoxide (NO), nitrogen dioxide (NO₂), nitric acid (HNO₃) andother oxygen-containing compounds.

The fourth, optional supply container 165 can store for example a secondoxidizing agent, such as NO₂, for instance. The fifth, likewise optionalsupply container 170 can store a further precursor gas, for example asecond metal carbonyl or a second main group element alkoxide. Finally,the sixth, optional supply container 175 can contain an etching gas.With the aid thereof, defects of excess material (dark defects) of thephotomask 105 can be repaired. Furthermore, the etching gas stored inthe sixth container 175 can be used to remove again too much materialdeposited on the mask 105 during a defect repair.

Each supply container 150, 155, 160, 165, 170, 175 has its own controlvalve 151, 156, 161, 166, 171, 176, in order to supervise or control theabsolute value of the corresponding gas that is provided per unit time,i.e. the gas volumetric flow rate at the location of the incidence ofthe electron beam 127. The control valves 151, 156, 161, 166, 171 and176 are controlled and supervised by the control unit 145 of thecomputer system 140. The partial pressure ratios of the gases providedat the processing site can thus be set in a wide range.

Furthermore, in the exemplary device 100 each supply container 150, 155,160, 165, 170, 175 has its own gas feed line system 152, 157, 162, 167,172, 177, which ends with a nozzle in the vicinity of the point ofincidence of the electron beam 127 on the photomask 105. In analternative embodiment (not represented in FIG. 1), a gas feed linesystem is used to bring a plurality or all of the processing gases in acommon stream onto the surface of the sample 105.

In the example illustrated in FIG. 1, the valves 151, 156, 161, 166,171, 176 are arranged in the vicinity of the corresponding containers150, 155, 160, 165, 170, 175. In an alternative arrangement, the controlvalves 151, 156, 161, 166, 171, 176 can be incorporated in the vicinityof the corresponding nozzles (not shown in FIG. 1). Unlike theillustration shown in FIG. 1 and without preference at the present time,it is also possible to provide one or a plurality of the gases stored inthe containers 150, 155, 160, 165, 170, 175 non-directionally in thelower part of the vacuum chamber 102 of the device 100. In this case, itis necessary for the device 100 to incorporate a stop (not illustratedin FIG. 1) between the lower reaction space and the upper part of thedevice 100, which provides the electron beam 127, in order to prevent anexcessively low vacuum in the upper part of the device 100.

Each of the supply containers 150, 155, 160, 165, 170 and 175 may haveits own temperature setting element and control element that enablesboth cooling and heating of the corresponding supply containers. Thismakes it possible to store and provide the carbon-containing precursorgases, the oxidizing agent(s) and, if appropriate, the etching gas atthe respectively optimum temperature (not shown in FIG. 1). Furthermore,each feeder system 152, 157, 162, 167, 172 and 177 may comprise its owntemperature setting element and temperature control element in order toprovide all the process gases at their optimum processing temperature atthe point of incidence of the electron beam 127 on the photomask 105(likewise not indicated in FIG. 1). The control unit 145 of the computersystem 140 can control the temperature setting elements and thetemperature control elements both of the supply containers 150, 155,160, 165, 170, 175 and of the gas feed line systems 152, 157, 162, 167,172, 177.

The device 100 in FIG. 1 comprises a pump system for generating andmaintaining a vacuum required in the vacuum chamber 102 (not shown inFIG. 1). With closed control valves 151, 156, 161, 166, 171, 176, aresidual gas pressure of ≤10⁻⁷ mbar is achieved in the vacuum chamber102 of the device 100. The pump system may comprise separate pumpsystems for the upper part of the device 100 for providing the electronbeam 127, and the lower part comprising the sample stage 110 with thephotomask 105. Furthermore, the device 100 can comprise a suctionextraction device in the vicinity of the processing point of theelectron beam 127 in order to define a defined local pressure conditionat the surface of the sample of the photomask 105 (not illustrated inFIG. 1). The use of an additional suction extraction device can largelyprevent one or a plurality of volatile reaction products of the one orthe plurality of carbon-containing precursor gases which are not neededfor the local deposition of the deposited material from depositing onthe photomask 105 and/or in the vacuum chamber 102. Furthermore, thesuction extraction device can prevent particles that arise in an etchingprocess from being distributed in the vacuum chamber 102 of the device100. The functions of the pump system(s) and of the additional suctionextraction device can likewise be controlled and/or monitored by thecontrol unit 145 of the computer system 140.

Finally, the device 100 can comprise one or more scanning forcemicroscopes that make it possible to analyze defects of the photomask indetail (not illustrated in FIG. 1).

FIG. 2 schematically shows an excerpt from the photomask 105. In theexample in FIG. 2, the photomask 105 may comprise a binary mask 210 or aphase mask 220, for example an attenuated phase shift mask. Furthermore,the photomask 105 may comprise a pure quartz mask or a mask fornanoimprint lithography (NIL). The pure quartz mask can be exposed withradiation in the wavelength range of 193 nm.

The upper part of FIG. 2 presents a plan view of part of the mask 105.The lower part represents a side view of the excerpt in the upper part.The photolithographic mask 105 comprises an optically transparentsubstrate 230, preferably a quartz substrate or a calcium fluoride(CaF₂) substrate. If the photomask 105 represents a binary mask 210, ablack or an opaque pattern 240 is arranged on the substrate 230. Thepattern 240 is represented by a line pattern 240 in the example in FIG.2. The material of the line pattern 240 often comprises chromium that istypically coated with a thin chromium oxide layer. Alternatively, it ispossible to use aluminum or titanium for producing a binary photomask210, which are likewise covered by a thin oxide layer (i.e. comprising afew nanometers). Typical absorber structures have layer thicknesses inthe range of 10 nm to 100 nm.

Binary masks 210 can also be produced with other absorber materials, forexample from a thick (d≈200 nm) non-transparent layer ofmolybdenum-silicon. Examples of further absorber materials are compoundsof molybdenum, nitrogen, silicon and oxygen, which in the technicalfield are abbreviated to OMOG, standing for Opaque MoSi On Glass, andcompounds of tantalum, boron and nitrogen. The layer thicknesses ofthese materials are typically in the region of 100 nm or less. A binarymask is distinguished by an absorber pattern whose structure dimensionsare larger than the diffraction limit of the radiation used for theexposure and whose optical transmission at the exposure wavelength is<1%.

Absorber elements of phase masks 220, for example the line pattern 250in FIG. 2, are often produced from partly transparent molybdenum siliconoxide (MoSiO_(x), 0<x≤1) or molybdenum silicon oxynitride (MoSiOxNy,0<x≤1, 0<y≤1). For phase masks having exposure wavelengths in the deepultraviolet wavelength range (248 nm or 193 nm), the elements of thestructure-producing layer are often produced from silicon nitride dopedwith molybdenum and oxygen in the single-digit percentage range.Hereinafter these phase shifting absorber layers are designated as MoSilayers.

However, chromium oxide (CrO) and/or chromium oxynitride (CrO_(x)N_(y),0<x≤1, o<y≤1) can also be used as absorber material for phase masks 220,for example attenuated phase shift masks. The layer thickness of thephase shifting and absorbing structure elements 250 of phase masks 220is adapted to the exposure wavelength used. Examples of further phasemasks are pure quartz structures of different heights, which arereferred to in the technical field as CPL, standing for chromeless phaseshifting lithography. Furthermore, phase masks composed of quartzstructures of different heights with a binary absorber are used, whichare abbreviated to APSM standing for alternating phase shift mask. Theprocesses for defect correction as described in this application can beapplied to all the mask types mentioned.

The photomask 105 in FIG. 2 has a defect 260 of absent material. Thedefect 260 denotes a depression in the transparent substrate 230 of thephotomask 105, i.e. material of the substrate 230 is absent at thelocation of the defect 260. After finding the defect 260 and/or furtherdefects 270, 280 (cf. FIGS. 5 and 7) with the aid of a correspondingmetrology tool (for example with a laser system), the defect 260 or thedefects 260, 270, 280 is or are scanned by the electron beam 127 of thedevice 100 in a first step. As necessary, the defect 260 or the defects260, 270, 280 can additionally be examined using a scanning forcemicroscope.

A photomask typically has a thickness of 6.35 mm. The defect 260 mayhave a depth of less than one nanometer up to a range of several hundrednanometers. The lateral dimensions of the defect 260 of absent substratematerial may extend from the single-digit nanometers range into thetwo-digit micrometers range. The defect 260 can be corrected bydepositing silicon dioxide (SiO₂) at the location of absent substratematerial. The precursor gases tetraethyl orthosilicate (TEOS) andtetramethyl orthosilicate (TMOS) can be used as SiO₂ suppliers bycleavage of the ligands. Preferably oxygen (O₂), or nitrogen dioxide(NO₂) is used as oxidizing agent for the repair of the defect 260. Inthe example described below, TEOS is used as precursor gas and NO₂ isused as oxidizing agent.

In order to repair the clear defect 260 or the substrate defect 260,from the supply container 150 TEOS is provided at the location of thedefect 260 by use of the feed line system 152 in a manner controlled bythe control valve 151. Then the TEOS is adsorbed onto the surface of thesubstrate 230 in the region of the defect location (physisorption). Withthe aid of the control valve 151, the pressure at the defect location isset to 10⁻⁵ mbar. This corresponds to a gas volumetric flow rate ofapproximately 0.05 sccm (standard cubic centimeter). The precursor gasTEOS is provided at the location of the defect 260 at a temperature of−10° C. At the same time, at the defect location, from the supplycontainer 160 the oxidizing agent NO₂ is supplied via the gas feed linesystem 162 at a gas volumetric flow rate of 4 sccm in a mannercontrolled by the control valve 161. The gas volumetric flow rate of theoxygen generates a partial pressure of pressure of 10⁻³ mbar at thedefect location. For repairing the clear defect 260, the precursor gasTEOS or more generally the main group element and the oxidizing as forexample NO₂ may be provided with a mixture ratio of 1:10. In the exampledescribed in the context of FIGS. 2 to 4, the clear defect 260 isrepaired with a gas volumetric flow rate of 4 sccm. For the defectcorrection described in FIGS. 6 to 8 a gas volumetric flow ratecomprises a range of 0.3 sccm to 10 sccm.

An electron beam 127 of the device 100 supplies locally at the locationof the defect 260 energy for initiating a local chemical reaction thatcleaves at least a portion of the ligands of the precursor gas TEOS fromthe latter's central atom silicon. The oxidizing agent NO₂ additionallyprovided locally supports, on the one hand, the oxidation of the centralatom of TEOS to SiO₂ and, on the other hand, the oxidation of thecleaved ligands or of the fragments thereof, which as volatilecomponents are extracted by suction from the vacuum chamber 102 by thesuction extraction device of the device 100. The oxidizing agent NO₂present in excess brings about the deposition of a purer SiO₂ layer atthe defect location, into which moreover less carbon is incorporated,compared with a process implementation without providing the oxygen atthe deposition location. In the layer deposited at the defect location,carbon is represented merely with ≤5 atom %.

During the deposition process, the electron beam 127 supplies electronshaving a kinetic energy of up to 1 keV and having a beam current ofapproximately 50 pA. The electron beam is raster-scanned over thelocation of the defect 260 with a focus diameter of 5 nm with arepetition duration of 1 ms and a dwell time of up to 1 μs.

Depending on the dimensions of the defect 260, the deposition process isinterrupted after a specific time duration and the remaining residue 360of the defect 260 is analyzed by use of the electron beam 127 and/or ascanning force microscope. This is illustrated in FIG. 3. A timeduration after which the deposition process has substantially repairedthe defect 260 with the aid of the precursor gas TEOS and the oxidizingagent NO₂ is calculated from the measurement data of the residue 360that remained.

FIG. 4 represents the excerpt from the photomask 105 from FIG. 3 afterthe end of the second deposition process step for repairing thesubstrate defect 260. The deposition process has substantiallyeliminated the depression, i.e. the defect 260, by depositing an SiO₂layer. On account of the low carbon proportion of the deposited layer460, it is expedient to choose the thickness of the deposited layer 460such that the latter precisely fills the depression of the defect 260.

If a small proportion of the defect 260 is still present after thesecond deposition process step, it can be corrected by a furthertemporally limited deposition of SiO₂. If too much material hasinadvertently been deposited laterally and/or vertically on thesubstrate 230 of the photomask 210, 220, it can be removed again afterthe analysis of the newly generated defect, with the aid of the electronbeam 127 and an etching gas, for example xenon difluoride (XeF₂), storedin the supply container 175.

In the example discussed in FIGS. 2 to 4, the defect 260 is a defect ofthe substrate 230 of a binary mask 210 or of a phase shifting mask 220.However, the deposition process described can also be used fordepositing absent material onto a phase mask that manages withoutstructure elements composed of absorber material, such as the CPL, ASPMand NIL masks described above.

FIG. 5 shows an excerpt from a binary phase mask 210 having absorberstructure elements 240 arranged on a substrate 230. FIG. 5 presents inthe upper partial illustration a plan view and in the lower partialillustration a side view of the excerpt from the binary photomask 210.In the example in FIG. 5, the absorber structure elements 240 areproduced from a chromium layer comprising a thin chromium oxide layer(comprising a few nanometers) at the surface. The thickness of thechromium layer is in the range of 10 nm to 100 nm. In FIG. 5, thecentral absorber structure element 240 has a defect 270, which denotes alocation of absent absorber material.

The repair of the defect 270 of the binary photomask 210 in FIG. 5 isdiscussed below. The lateral dimensions of the defect 270 may range fromthe single-digit nanometers range to the two-digit micrometers range.The defect 270 of the absorber structure 240 can be corrected reliablywith the aid of a metal carbonyl and an oxidizing agent. In the exampledescribed here, chromium hexacarbonyl is used as precursor gas and NO₂is used as oxidizing agent. Instead of chromium hexacarbonyl, anothermetal carbonyl can be used, as for example molybdenum hexacarbonyl(Mo(CO)₆), tungsten hexacarbonyl (W(CO)₆), dicobalt octacarbonyl(Co₂(CO)₈), triruthenium dodedecarbonyl (Ru₃(CO)₁₂) or ironpentacarbonyl (Fe(CO)₅). The metal carbonyl, i.e. the precursor gas andthe NO₂ used as oxidizing agent can be provided at the defect 270 of theabsorber structure 240 with a mixture ratio of 1:10.

In order to repair the defect 270 of the absorber structure element 240of the binary mask 210, from the supply container 155 the precursor gaschromium hexacarbonyl (Cr(CO)₆) is supplied to the location of thedefect 270 by use of the gas feed line system 157. The Cr(CO)₆ isadsorbed on the surface of the substrate 230 in the region of the defect270. The control unit 145 of the computer system 140 opens the controlvalve 156 of the supply container 155 in order to generate a gaspressure of the Cr(CO)₆ at the location of the defect of 5·10⁻⁴ mbar.This corresponds to a gas volumetric flow rate of 0.01 sccm.Simultaneously, at the defect location, from the supply container 165the oxidizing agent NO₂ is provided via the gas feed line system 167 ata gas volumetric flow rate of 2 sccm in a manner controlled by the gasfeed line system 167 and the control valve 166. The NO₂ gas volumetricflow rate generates a partial pressure of 5·10⁻² mbar at the defectlocation.

The electron beam 127 of the device 100 supplies locally at the locationof the defect 270 energy which, in a local chemical reaction, separatesat least a portion of the CO ligands of the precursor gas Cr(CO)₆ fromthe latter's central atom chromium (Cr). The oxidizing agent NO₂additionally provided locally supports the dissociation of the ligandsof the Cr(CO)₆, promotes the oxidation of the central atom Cr to CrO, inparticular to CrO₂, and facilitates the oxidation of the dissociated COligands to carbon dioxide (CO₂), which as volatile components can beextracted by suction from the vacuum chamber 102 by the suctionextraction device of the device 100. In comparison with a depositionprocess without additionally providing NO₂ at the location of the defect270, the NO₂ excess leads to the deposition of a purer Cr/CrO layer atthe defect location. Since the overwhelming majority of the cleaved COligands can be removed as CO₂ from the vacuum chamber 102 of the device100, drastically less carbon is incorporated into the deposited layer.The deposited layer comprises only about 5 atom % of carbon.

In order to initiate the deposition process, the electron beam 127provides electrons having a kinetic energy of 1 keV and having a currentintensity of approximately 40 pA. The electron beam 127 israster-scanned over the location of the defect 270 with a focus diameterof 5 nm with a repetition time of 1 ms and a dwell time of 1 μs.

The repair process can be performed—as explained above—once again in aplurality of successive steps. Between the individual deposition steps,the residue of the defect 270 that still remained is analyzed by use ofthe electron beam 127 and/or a scanning force microscope and the timeduration for the next deposition step is thereby determined. FIG. 6shows the layer 670 deposited at the location of the defect 270. Theheight of the deposited material 670 is adapted to the height of theabsorber elements 240. This is advantageous owing to the similar opticalproperties of the absorber structure elements 240 and of the material ofthe deposited layer 670.

Between the individual repair steps, the partial pressure ratio of themetal carbonyl Cr(CO)₆ and of the oxidizing agent NO₂ can be adapted. Itis furthermore possible to provide the precursor gas and/or theoxidizing agent continuously or in a pulsed manner at the location ofthe defect 270 during the deposition process.

Each electron supplied by the electron beam 127 leads to the depositionof a volume of 0.05 Å³ to 0.25 Å³. This corresponds to a deposition rateof approximately 0.1 nm/s. As already mentioned above, the layerthickness of the absorber elements 240 is in the range of 10 nm to 100nm. A Cr/CrO layer having a thickness of 60 nm can thus be deposited ina time interval of approximately 10 minutes.

The examples discussed in the context of FIGS. 2 to 6 relate to therepair of absent material of binary 210 or phase shifting transmissivephotomasks 220. However, the repair process described can also be usedfor repairing absent material of absorber elements of photomasks for theextreme ultraviolet (EUV) wavelength range. In the case of EUV masks,absorber structure elements are often produced from chromium or tantalumnitride (TaN). By choosing a corresponding metal carbonyl and anoxidizing agent, for instance oxygen or nitrogen dioxide, it is possibleto repair defects of absent absorber material in EUV masks. Chromiumlayers can be repaired—as already explained above—for example by the useof the precursor gas chromium hexacarbonyl (Cr(CO)₆) and tantalumnitride layers can be repaired for example with the aid of the precursorgas tantalum hexacarbonyl (Ta(CO)₆). Alternatively, titaniumtetraisoproproxide (Ti(OCH(CH₃)₂)₄) can be used for repairing cleardefects of TaN absorber structure elements.

In a further application example, the photomask 220 in FIG. 7 describesa phase shifting mask whose absorber elements 250 comprise a thin partlytransmissive MoSi layer (attenuated phase shift mask). In the example inFIG. 7, the MoSi layer of an absorber element 250 has the defect 280 ofabsent absorber material. The defect 280 of the MoSi absorber element250 can be corrected by simultaneously depositing silicon dioxide (SiO₂)and a metal at the location of absent absorber material. In this case,TEOS and/or TMOS can be used as precursor gases supplying SiO₂, and ametal carbonyl can be used as a precursor gas supplying metal. Onceagain use is preferably made of O₂ and/or NO₂ as oxidizing agent for therepair of the defect 280 of the MoSi absorber element 250.

In order to correct the defect 280 of absent absorber material, from thesupply container 150 TEOS is provided at the location of the defect 280by use of the feed line system 152 in a manner controlled by the controlvalve 151. With the aid of the control valve 151, the pressure at thedefect location is set to 10⁻⁵ mbar. The precursor gas TEOS is at atemperature of −10° C. at the location of the defect 280. At the sametime, at the defect location, from the supply container 155 chromiumhexacarbonyl is brought to the location of the defect 280 in a mannercontrolled by the control valve 156 and the gas feed line system 157. Atthe location of the defect 280, the Cr(CO)₆ is at a temperature of −20°C. The control valve 156 is opened to an extent such that the partialpressure of the precursor gas Cr(CO)₆ reaches 5·10⁻⁶ mbar. In theexample under discussion, the precursor gases have a partial pressureratio TEOS:Cr(CO)₆ of 5:1. The two precursor gases coadsorb in theregion of the defect 280 on the surface of the substrate 230 of thephase shifting photomask 220. The defect 280 may be corrected byproviding one or more metal carbonyl in a temperature range of −50° C.to +35° C. The main group element alkoxide (TEOS for correcting thedefect 280) is provided at the defect location having a temperature inthe range of −40° C. to +15° C.

In parallel with the precursor gases TEOS and Cr(CO)₆, from the supplycontainer 165 the oxidizing agent NO₂ is passed to the location of thedefect 280 via the gas feed line system 167 at a gas volumetric flowrate of 2.5 sccm in a manner controlled by the control valve 166. Thegas volumetric flow rate of the NO₂ generates a partial pressure of 10⁻²mbar at the defect location. Generally, for correcting the defect 280,one or more metal carbonyl is provided in a pressure range of 10⁻⁶ mbarto 10⁻⁴ mbar. Further, one or more main group element alkoxides isprovide at the location of the defect 280 in a pressure range of 10⁻⁶mbar to 10⁻⁴ mbar. Moreover, the local chemical defect correctionreaction is carried out by providing at least one of the oxidizingagents in a pressure range of 10⁻⁵ mbar to 10⁻² mbar.

An electron beam 127 of the device 100 initiates locally at the locationof the defect 280 a chemical reaction that cleaves at least a portion ofthe ligands of the precursor gas TEOS from the latter's central atomsilicon. Furthermore, the local chemical reaction simultaneously bringsabout a dissociation of the CO ligands from the central atom chromium ofthe chromium hexacarbonyl. The NO₂ additionally provided locally fostersthe oxidation of the silicon central atom of TEOS to SiO₂, the oxidationof the chromium central atom of Cr(CO)₆ and the oxidation of the cleavedligands or of fragments of the ligands. In particular, the nitrogendioxide present in excess promotes the oxidation of the CO ligands tovolatile CO₂. The volatile components that arose during thedecomposition of the precursor gases are removed from the vacuum chamber102 by the suction extraction device of the device 100.

In order to initiate the local chemical reaction, the electron beam 127is scanned over the location of the defect 270 with a focus diameter of5 nm with a repetition time of 1 ms and a dwell time of 1 μs. Theelectrons of the electron beam 127 impinge on the surface of thesubstrate 230 of the photomask 220 with a kinetic energy of 1 keV at thedefect location. The current intensity of the electron beam 127 is inthe region of approximately 50 pA.

FIG. 8 shows the excerpt from the phase mask 220 from FIG. 7 after therepair of the defect 280. The layer 870 was deposited at the location ofsaid defect. The height of the deposited layer 870 substantiallycorresponds to the thickness of the MoSi structure elements 250.

The oxidation of the precursor gases during the deposition process leadsto a reduction of the carbon proportion in the deposited materialcompared with the carbon proportion of the precursor gases used. As aresult, the oxidizing agent NO₂ in combination with the precursor gasesTEOS and Cr(CO)₆ brings about the deposition of a carbon-poor SiO₂/Crlayer at the location of the defect 280. The carbon proportion of thelayer deposited at the defect location is ≤5 atom %.

The temporal sequence of the deposition process is described above inthe context of the discussion of FIGS. 2 to 4.

The repair of an MoSi structure element 250 of a phase mask 220 isexplained in FIGS. 7 and 8. As already indicated above, the absorberstructure elements 240 of a binary photomask 210 can likewise beproduced from a thick non-transparent MoSi layer. The process forrepairing a partly transmissive thin MoSi layer as explained in thecontext of FIGS. 7 and 8 can, of course, also be used for correcting adefect of absent material of a thick non-transmissive MoSi layer.

In the prior art, the defects 280 of phase shifting MoSi layers 250 aredeposited by the progressive application of an SiO₂ layer from TEOS anda chromium layer from Cr(CO)₆. According to the theory, the phaseshifting effect is ascribed principally to the layer deposited from theprecursor gas TEOS and the absorbing effect is ascribed predominantly tothe layer deposited from the precursor gas Cr(CO)₆. Typically, in theprior art in order to repair defects 280 of MoSi layers, depositedmaterials having a layer thickness significantly greater than thesurrounding MoSi layer are deposited. Therefore, in the case ofphotomasks 220 having feature sizes of <150 nm, in the region of therepaired location, deviations in the exposure of a wafer can occurcompared with a defect-free reference location.

The intermixing of the two precursor gases at the reaction location,i.e. at the location of the defect 280, with simultaneous oxidation bythe oxidizing agent utilizes the phase shifting and the absorbingproperties of all the reactants. A separation into a phase shiftinglayer and an absorbing layer is cancelled as a result. Moreover, theoxidation of both precursor gases results in a deposited material at therepaired location which has a very low carbon proportion. For thisreason, the repaired location of the MoSi absorber structure element 250is not subject to significant ageing and in particular exhibitslong-term stability in relation to mask cleaning processes and also theexposure doses which occur during the use of the repaired photomask 210,220. The process—described in the prior art—of applying a metallicprotective layer above the repaired location of the absorber element 250of the phase mask 220 can be omitted. As a result, the method describedin this application significantly simplifies the repair of absentmaterial.

If the exemplary repair processes described above in the context of thediscussion of FIGS. 2 to 8 are performed without providing an oxidizingagent, then the deposited layers have a carbon proportion of 20 atom %or more. During exposure with high-energy deep ultraviolet light (λ=193nm), photomasks are subjected to an enormous loading. The radiation doseduring the exposure of a wafer is very much greater than 100 kJ/cm². Asa result of the extremely high exposure doses, in the extremely cleanand dry environment of photolithographic exposure apparatuses (XCDA(eXtra Clean Dry Air) atmosphere), the formation of ozone can occur,ozone being known as a particularly good oxidizing agent for carbon orcarbon compounds. The carbon incorporated into the deposited layers atthe locations of the repaired defects 260, 270, 280, or the incorporatedcarbon compounds, such as CO ligands, for example, react with the ozoneto form CO₂, which escapes from the deposited material and thus weakensthe structure thereof.

Furthermore, modern cleaning agents for photomasks 210, 220 areparticularly effective on carbon-containing compounds. As a result, inthe context of the mask cleaning that regularly takes place, carbon orcarbon-containing constituents is/are extracted from the layersdeposited for defect correction. This leads firstly to a change in theoptical properties of the deposited materials and secondly to aweakening of the structure thereof. In total, therefore, materialsdeposited on a photomask 210, 220 are subject to ageing if they aredeposited without additional oxidizing agent.

The flow diagram 900 in FIG. 9 represents steps of the method forpermanently repairing defects 260, 270, 280 of absent material of aphotolithographic mask 105, 210, 220. The optional method steps arerepresented by a dashed frame in the diagram 900.

The method starts at step 905. Step 910 involves examining the defect260, 270, 280 or the identified defects 260, 270, 280 of absent materialwith the aid of an electron beam 127 and/or a probe of a scanning forcemicroscope. Step 915 involves providing at least one carbon-containingprecursor gas and at least one oxidizing agent at the defective location260, 270, 280 of the photolithographic mask 105, 210, 220.

In step 920, an energy source, for example the electron beam 127,initiates a local chemical reaction of the at least onecarbon-containing precursor gas at the location of absent material inorder to deposit absent material at the defective location 260, 270,280, wherein the deposited material 460, 670, 880 comprises at least onereaction product of the reacted at least one carbon-comprising precursorgas.

Step 925 comprises controlling a gas volumetric flow rate of the atleast one oxidizing agent in order to minimize a carbon proportion ofthe deposited material 460, 670, 880. The gas volumetric flow rate ofthe oxidizing agent can be implemented by a control unit 145 inconjunction with control valves 151, 156, 161, 166, 171, 176.

Step 930 involves examining the residual defect 360. Decision step 935then involves deciding whether the residual defect 360 is less than orequal to a predefined threshold value. If this is the case, the methodends at step 940. If this is not the case, the method proceeds to step915 and starts a second deposition process step.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular embodiments of particular inventions.Certain features that are described in this specification in the contextof separate embodiments can also be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults.

Thus, particular embodiments of the subject matter have been described.Other embodiments are within the scope of the following claims. In somecases, the actions recited in the claims can be performed in a differentorder and still achieve desirable results.

What is claimed is:
 1. A method for repairing defects of absent materialof a photolithographic mask, wherein the method comprises the followingsteps: a. providing at least one carbon-containing precursor gas and atleast one oxidizing agent at a location to be repaired of thephotolithographic mask, in which the at least one carbon-containingprecursor gas comprises a mixture of at least one metal carbonyl and atleast one main group element alkoxide at the location to be repaired; b.initiating a reaction of the at least one carbon-containing precursorgas with the aid of at least one energy source at the location of absentmaterial in order to deposit material at the location of absentmaterial, wherein the deposited material comprises at least one reactionproduct of the reacted mixture of the at least one metal carbonyl andthe at least one main group element alkoxide, and controlling a gasvolumetric flow rate of the mixture of the at least one metal carbonyland the at least one main group element alkoxide to cause the materialto be deposited at a rate of 0.01 nm/s to 1.0 nm/s; and c. controllingthe gas volumetric flow rate of the at least one oxidizing agent inorder to reduce a carbon proportion of the deposited material, whereinthe deposited material comprises a carbon proportion of <20 atom %; d.wherein the deposited material withstands a radiation dose during anexposure of more than 100 kJ/cm² and at least 10 cleaning cycles withouta change in its optical properties and its dimensions.
 2. The methodaccording to claim 1, wherein the deposited material comprises a carbonproportion of <15 atom %.
 3. The method according to claim 1, whereinthe at least one metal carbonyl comprises at least one element from thegroup: chromium hexacarbonyl (Cr(CO)₆), molybdenum hexacarbonyl(Mo(CO)₆), tungsten hexacarbonyl (W(CO)₆), dicobalt octacarbonyl(Co₂(CO₈), triruthenium dodecacarbonyl (Ru₃(CO)₁₂), and ironpentacarbonyl (Fe(CO)₅).
 4. The method according to claim 1, wherein theat least one main group element alkoxide comprises at least one elementfrom the group: tetraethyl orthosilicate (Si(OC₂H₅)₄), tetramethylorthosilicate (Si(OCH₃)₄) and titanium tetraisopropoxide(Ti(OCH(CH₃)₂)₄).
 5. The method of claim 4 in which the depositedmaterial comprises metal atoms and Si, and wherein step b. comprisescontrolling the gas volumetric flow rate of the mixture of the at leastone metal carbonyl and the at least one main group element alkoxide tocause the material comprising metal atoms and Si to be deposited at arate of 0.01 nm/s to 1.0 nm/s.
 6. The method of claim 4 in which thedeposited material comprises metal atoms and Ti, and wherein step b.comprises controlling the gas volumetric flow rate of the mixture of theat least one metal carbonyl and the at least one main group elementalkoxide to cause the material comprising metal atoms and Ti to bedeposited at a rate of 0.01 nm/s to 1.0 nm/s.
 7. The method according toclaim 1, wherein the at least one oxidizing agent comprises at least oneelement from the group: oxygen (O₂), ozone (O₃), water vapor (H₂O),hydrogen peroxide (H₂O₂), dinitrogen monoxide (N₂O), nitrogen monoxide(NO), nitrogen dioxide (NO₂) and nitric acid (HNO₃).
 8. The methodaccording to claim 1, wherein the at least one energy source comprisesat least one particle beam.
 9. The method according to claim 1, whereinthe absent material comprises at least one element from the group:absent material of at least one structure element of a binary mask,absent material of at least one structure element of a phase mask,absent material of at least one structure element of a photomask for theextreme ultraviolet wavelength range, absent material of a substrate ofa transmissive photolithographic mask, and absent material of at leastone structure element of a nanoimprint lithography mask.
 10. The methodaccording to claim 1, wherein providing the at least one precursor gasand the at least one oxidizing agent at the location of absent materialis carried out with a mixture ratio of 1:10.
 11. The method according toclaim 1, wherein providing the at least one metal carbonyl and the atleast one main group element alkoxide is carried out with a mixtureratio of 1:5.
 12. The method according to claim 1, wherein providing theat least one main group element alkoxide and the at least one oxidizingagent at the location of absent material is carried out with a mixtureratio of 1:10.
 13. The method according to claim 1, wherein providingthe at least one oxidizing agent is carried out with a gas volumetricflow rate in the range of 0.3 sccm to 10 sccm.
 14. The method accordingto claim 1, wherein providing the at least one metal carbonyl at thelocation of absent material is carried out in a pressure range of 10⁻⁶mbar to 10⁻⁴ mbar, providing the at least one main group elementalkoxide is carried out in a pressure range of 10⁻⁶ mbar to 10⁻⁴ mbar,and/or providing the at least one oxidizing agent is carried out in apressure range of 10⁻⁵ mbar to 10⁻² mbar.
 15. The method according toclaim 1, wherein providing the at least one metal carbonyl at thelocation of absent material is carried out in a temperature range of−50° C. to +35° C.
 16. The method according to claim 1, whereinproviding the at least one main group element alkoxide at the locationof absent material is carried out in a temperature range of −40° C. to+15° C.
 17. The method according to claim 1, wherein thephotolithographic mask comprises a phase mask, and providing the atleast one precursor gas comprises simultaneously providing chromiumhexacarbonyl (Cr(CO₆)) and tetraethyl orthosilicate (Si(OC₂H₅)₄). 18.The method of claim 1 in which the at least one energy source comprisesan electron beam that has a resolution in a range of 0.4 nm to 10 nm.19. A method for repairing defects of absent material of aphotolithographic mask, the method comprising: a. providing a mixture ofat least one metal carbonyl, at least one main group element alkoxide,and at least one oxidizing agent at a location to be repaired of thephotolithographic mask; and b. initiating a reaction of the at least onemetal carbonyl and the at least one main group element alkoxide with theaid of at least one energy source at the location of absent material inorder to deposit material at the location of absent material, whereinthe deposited material comprises at least one reaction product of thereacted mixture of the at least one metal carbonyl and the at least onemain group element alkoxide, and controlling a gas volumetric flow rateof the mixture of the at least one metal carbonyl, the at least one maingroup element alkoxide, and the at least one oxidizing agent to causethe material to be deposited at a rate of 0.01 nm/s to 1.0 nm/s; c.wherein the deposited material is configured to withstand a radiationdose during an exposure of more than 100 kJ/cm² and at least 10 cleaningcycles without a change in its optical properties and its dimensions.20. The method of claim 19, comprising controlling the gas volumetricflow rate of the at least one oxidizing agent in order to reduce acarbon proportion of the deposited material to be less than 15 atom %.21. The method of claim 19 in which the at least one energy sourcecomprises an electron beam that has a resolution in a range of 0.4 nm to10 nm.
 22. The method of claim 19 in which the at least one main groupelement alkoxide comprises at least one element from the group:tetraethyl orthosilicate (Si(OC₂H₅)₄), tetramethyl orthosilicate(Si(OCH₃)₄) and titanium tetraisopropoxide (Ti(OCH(CH₃)₂)₄).
 23. Themethod of claim 22 in which the deposited material comprises metal atomsand Si, and wherein step b. comprises controlling the gas volumetricflow rate of the mixture of the at least one metal carbonyl and the atleast one main group element alkoxide to cause the material comprisingmetal atoms and Si to be deposited at a rate of 0.01 nm/s to 1.0 nm/s.24. The method of claim 22 in which the deposited material comprisesmetal atoms and Ti, and wherein step b. comprises controlling the gasvolumetric flow rate of the mixture of the at least one metal carbonyland the at least one main group element alkoxide to cause the materialcomprising metal atoms and Ti to be deposited at a rate of 0.01 nm/s to1.0 nm/s.